It is well known that cattle feed consisting of or including soybean meal made from roasted soybeans can increase the amount of protein escaping degradation (bypass protein) in the rumen of lactating dairy cows, thereby enhancing the nutritional value of such cattle feed. However, insufficient roasting of the soybeans results in a diet supplement which is little or no better than meal produced from untreated soybeans, whereas over roasting of the beans does not enhance their nutritional value but does result in increased costs resulting from the excess roasting time and fuel consumption.
A test procedure has been established to enable the bypass protein content in roasted soybeans to be determined. The test results are expressed in terms of the protein dispersibility index (PDI). A PDI of between 9.0 and 11.0 is achieved when the roasting is optimum.
A principal object of apparatus and methods according to the invention is to provide for the roasting of soybeans or other legumes in such manner as to effect optimum enhancement of the nutritional value or PDI thereof.